1. Field of the Invention
This invention relates to a method of and apparatus for determining position of an article, e.g. glass sheet relative to a reference position.
2. Discussion of the Prior Art
Light generating and detecting apparatus, i.e., photo sensing apparatus are taught in the prior art. For example, U.S. Pat. Nos. 2,220,736; 2,662,633; 3,108,727 and 3,495,089 teach the use of photo sensing apparatuses for orienting, detecting and/or sensing the position of articles, e.g., cleats and webs. U.S. Pat. Nos. 3,489,909; 3,656,854 and 4,053,234 teach the use of photo sensing apparatuses for inspecting physical properties of material, e.g., internal defects in glass; sheet thicknesses and/or induced surface fractures. Although photo sensing apparatuses are used in the above-mentioned technologies, the use of photo sensing apparatuses in combination with industrial robots to move or orient articles, e.g., sheets is relatively unexplored.
Industrial robots, e.g., as taught in U.S. Pat. No. 3,958,682 are responsive to chain driven signal generators for tracking the advance of work pieces to act on the work pieces. For example, a sheet engaging frame of the type taught in U.S. Patent Application Ser. Nos. 901,944, filed May 1, 1978 in the name of William P. Cathers for "Sheet Orienting and Transporting Frame" and Ser. No. 902,003, filed on May 1, 1978 in the names of William P. Cathers and Charles W. Dorn, Jr. for "Frame Having Rotating and Orienting Members" are mounted on a robot arm. When the sheet is in a given position e.g., as indicated by a chain driven signal generator, the frame engages the sheet to align the sheet. Thereafter the sheet is engaged by the frame and loaded in a shipping container. The sheet is aligned by retractable side members mounted on the frame.
Although the frame and robot combination of the prior art as taught in the above-mentioned patent applications are acceptible, it would be advantageous to employ a noncontacting system for locating a sheet and thereafter programming a robot to reorientate the path of the frame to pickup the sheet. In this manner, any edge damage that may result from contact between edges of the sheet and engaging side members of the prior art frames would be eliminated.